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‎.metadata/.plugins/org.eclipse.core.resources/.history/52/7071226f14a8001715918e2c1fc31ded‎

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package minimal_spanning_tree;
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public class TestMSTPrim {
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public static void main(String[] args) {
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MSTPrim mst=new MSTPrim();
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mst.createGraph();
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mst.getWeightArray();
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//mst.printWeightGraph();
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mst.mstprim(5);
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}
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}

‎.metadata/.plugins/org.eclipse.core.resources/.history/70/e057850a15a8001715918e2c1fc31ded‎

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package minimal_spanning_tree;
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import java.io.InputStream;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.Scanner;
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/**
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* 最小生成树的prim算法，从一个节点出发，每次找到与所有加入的节点相邻的节点，
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* 权重最小的节点(之前没有加入过)加入，不能形成环。
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*
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* @author liyafei
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*
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*/
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public class MSTPrim {
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List list = new ArrayList<>();
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int count = 1;
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double[][] weights;
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class Node {
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Node link;
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Node pre;
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int weight;
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int key;
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int start;
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int end;
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}
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/**
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* prim 算法求最小生成树,给定根节点，开始找相邻节点的最小值，算法每一步在连接集合A和A之外的节点的所有边中 选择一条轻量级边加入到A中
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* 用一个列表将遍历过的轻量级边的节点存储起来，然后看新的轻量级边的两点是否在列表中，如果在，就不加入。
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*
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* @param r 起始节点 注 意：图的矩阵表示形式是对称的，可以利用
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*/
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public void mstprim(int r) {
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List list2 = new ArrayList<>();
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// for (int i = 0; i < weights.length; i++) {
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// Node node = (Node) list.get(i);
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// node.key = Integer.MAX_VALUE;
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// node.pre = null;
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// }
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// // Node node=(Node) list.get(r);
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// node.key=0;
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// double[] arr=weights[r-1]; //取出给定顶点相邻节点的权重值，然后找出几行几列。排序
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// double min = Double.MAX_VALUE;
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// int index=0; //角标值
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// for (int i = 0; i < arr.length; i++) {
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// if(arr[i]>0 && arr[i]<min){
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// min=arr[i];
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// index=i;
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// }
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// }
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// (r,index)这条线被包括进来了
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// list2.add(r);
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// if(!list2.contains(index)){
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// list2.add(index);
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// }
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// Map map = new HashMap();
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list2.add(r);
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List list3 = new ArrayList<>();
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while (list2.size() < list.size()) {
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double minest = Double.MAX_VALUE;
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int index2 = 0;
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// List list4=new ArrayList<>();
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int[] arr = new int[2];
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for (int i = 0; i < list2.size(); i++) {
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double[] arr2 = weights[(int) list2.get(i)];
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int key = (int) list2.get(i);
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for (int j = 0; j < arr2.length; j++) {
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if (arr2[j] > 0 && arr2[j] < minest) {
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// System.out.println("j "+j);
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// System.out.println("arr2 "+arr2[j]);
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if (!list2.contains(j)) {
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minest = arr2[j];
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index2 = j;
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// map.put(key, index2);
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// 找个数据结构将（key,index2）存储起来
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arr[0] = key;
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arr[1] = index2; //key是最小生成树的上一节点（从遍历过的所有节点中选出），index2最小生成树的下一节点。
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// list4.add(key);
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// list4.add(index2);
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// System.out.println(index2);
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}
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}
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}
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}
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list3.add(arr);// 存储路径，里面使用列表存储了经过的路径（key,index2）
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list2.add(index2);
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}
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// double[] weis=weights[index];
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// double[][] afteriter=new double[2][weights.length];
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// afteriter[0]=arr;
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// afteriter[1]=weis;
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for (int i = 0; i < list2.size(); i++) {
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// System.out.println("key " + list2.get(i));
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// System.out.println("value "+map.get(list2.get(i)));
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}
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double sum = 0;
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int index3;
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int index4;
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System.out.println("最小生成树经过的路径为");
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for (int i = 0; i < list3.size(); i++) {
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// index3=(int) list2.get(i);
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// index4=(int) list2.get((i+1));
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// sum=sum+weights[index3][index4]; //总路径
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int[] arr = (int[]) list3.get(i);
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index3 = arr[0];
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index4 = arr[1];
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sum = sum + weights[index3][index4];
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System.out.println("从节点"+index3+"到节点"+index4+", 长度为"+weights[index3][index4]);
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}
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System.out.println("总的最短路径为"+sum);
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// System.out.println(list2.size());
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// System.out.println(min);
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// System.out.println(index);
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//
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}
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/**
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* 得到创建的带有权重的图，读出相邻节点之间的距离，然后存储到二维数组weights中。
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* 权重图的大小比节点多1，但是角标为0的位置都没用，为了处理存储的位置与节点的编号相一致
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*/
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public double[][] getWeightArray() {
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weights = new double[list.size()][list.size()];
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for (int i = 0; i < list.size(); i++) {
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Node node = (Node) list.get(i);
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while (node != null) {
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int row = node.start - 1;
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int col = node.end - 1;
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double weight = node.weight;
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weights[row][col] = weight;
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node = node.link;
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}
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}
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return weights;
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}
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/**
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* 打印权重图
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*/
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public void printWeightGraph() {
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double[][] weightsArray = getWeightArray();
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for (int i = 0; i < weightsArray.length; i++) {
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double[] wa = weightsArray[i];
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for (int j = 0; j < wa.length; j++) {
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System.out.print(wa[j] + " ");
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}
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System.out.println();
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}
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System.out.println();
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}
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/**
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* 先构建带有权重的无向图。
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*/
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public List createGraph() {
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Class clazz = this.getClass();
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InputStream ins = clazz.getResourceAsStream("/data.txt");
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Scanner scanner = new Scanner(ins);
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while (scanner.hasNextLine()) {
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String s1 = scanner.nextLine();
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Scanner oneLine = new Scanner(s1);
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Node newNode;
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Node first = null;
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Node last = null;
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while (oneLine.hasNext()) {
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String s2 = oneLine.next();
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int end = Integer.parseInt(s2);
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if (end == 999) {
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break;
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}
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newNode = new Node();
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if (first != null && oneLine.hasNext()) {
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String s3 = oneLine.next();
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int weight = Integer.parseInt(s3);
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newNode.weight = weight;
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}
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newNode.start = count;
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newNode.end = end;
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newNode.link = null;
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if (first == null) {
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first = newNode;
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last = newNode;
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} else {
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last.link = newNode;
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last = newNode;
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}
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}
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list.add(first);
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count++;
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}
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return list;
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}
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}

‎.metadata/.plugins/org.eclipse.core.resources/.history/78/90570a6814a8001715918e2c1fc31ded‎

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
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package minimal_spanning_tree;
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public class TestMSTPrim {
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public static void main(String[] args) {
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MSTPrim mst=new MSTPrim();
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mst.createGraph();
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mst.getWeightArray();
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mst.printWeightGraph();
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mst.mstprim(5);
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}
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}

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